The invention relates to novel synergistic compositions which selectively control tumor tissue, while healthy tissue is virtually unattacked. The novel compositions are therefore outstandingly suitable for cancer therapy.
Medicaments according to the prior art which are employed in chemotherapy as a rule only achieve partial success, i.e. they do not lead to a final cure. Moreover, the substances employed in the prior art frequently act only in a certain tumor category. A further disadvantage of the currently known chemotherapeutics are their often harmful side effects, as chemotherapeutics can generally have a cytostatic effect on proliferating tissue. The known chemotherapeutics are also unsatisfactory in the control of metastasis formation, and this is one of the main reasons which has until now prevented a decisive outcome in cancer therapy.
The fact that tumor tissue in an extracellular medium has a lowered average pH of about 6.5 to 7.0 and the pH can even fall to 5 on the cancer cell surface, while the pH in the normal tissue and in the blood is approximately 7.2 to 7.5, is known and described, for example, in DE-A 44 07 484 and in Tumor Biol., 1994, 15: 304-310. Thus each type of tumor has an intrinsic average intercellular pH, which, for example, in the case of breast tumors is about 6.7 and in the case of colon tumors about 6.9.
In the abovementioned publications, it is disclosed that due to the lowering of the pH range in tumor cells the natural immune defense is blocked, as the body""s own defense cells react to cancer target cells with full cytotoxicity only in a slightly basic medium of pH more than 7. DE-A 44 07 484 therefore proposes to bring the acidic external medium of cancer cells to the normal physiological pH level of 7 to 7.5 and thereby to control the cancer cells by means of the body""s own immune defense. For this purpose, the acidic external medium of cancer cells is brought to a physiological pH of 7 to 7.5 either by artificial basification measures or by the prevention of the acidification process itself.
The medicaments described in DE-A 44 07 484 admittedly represent an advance in cancer therapy, it would be desirable, however, to have available medicaments which besides the body""s own immune defense selectively control tumor cells and thus can be used as relatively low-side-effect chemotherapeutics.
Accordingly, WO 96/30003 proposes to use those compounds for the control of tumor tissue which, at a pH of less than 7, are protonated or release a substance, the protonated compound or the released substance having a more strongly destructive effect on cells than the unprotonated compound or the compound before release of the substance. For these compounds, WO 96/30003 discloses general formulae under which come a multiplicity of chemical compounds. Inter alia, 4-amino-2-hydroxybenzoic acid is mentioned as being effective there. Acetylsalicylic acid is also mentioned as a possible active compound, but this compound is not preferred.
The compounds of WO 96/30003 and also the mixtures generally proposed there of two and more compounds admittedly do already have a good anti-tumor effect, but, as before, there is a need for medicaments which have an improved anti-tumor effect, in particular at pH values of 7.0 or below, in particular in the range from 6.5 to 7.0.
It is therefore an object of the present invention to make available novel medicaments which have a strong cytotoxic effect which is largely selective on tumor tissue, in particular in a pH range from approximately 6.5 to approximately 7.0.
This object is solved by the subject of the patent claims.
The compositions according to the invention in principle act in the same manner as the benzoic acid derivatives disclosed in WO 96/30003. It has been shown, however, that these benzoic acid derivatives, which are known from WO 96/30003, do not have completely satisfactory activity against tumor tissue. Surprisingly, however, individual benzoic acid derivatives as a mixture with one another have a very strongly synergistic action for the destruction of tumor tissue and in a pH range of approximately 7.0 and below cause a virtually complete cell death in tumor tissue.
The compositions according to the invention are mixtures which contain at least two of the following benzoic acid derivatives or cinnamic acid derivatives, respectively, which act synergistically as a mixture with one another:
2-acetoxybenzoic acid (acetylsalicylic acid, Aspirin(copyright))
2-hydroxybenzoic acid
2-methoxybenzoic acid
2,4-dihydroxybenzoic acid
2,4-diacetoxybenzoic acid
2-hydroxy-4-aminobenzoic acid
2,4-dimethoxybenzoic acid
2,6-dihydroxybenzoic acid
2,6-dimethoxybenzoic acid
2,3,4-trimethoxybenzoic acid
2,4,6-trihydroxybenzoic acid
2,4,6-trimethoxybenzoic acid
5-(2,4-difluoro-phenyl)salicylic acid
xcex1-cyano-3-hydroxycinnamic acid
xcex1-cyano-4-hydroxycinnamic acid
xcex1-fluorocinnamic acid
xcex1-methylcinnamic acid and
xcex1-acetamidocinnamic acid.
Preferably, the mixture contains at least two of the following benzoic acid derivatives, which act synergistically as a mixture with one another:
2-acetoxybenzoic acid (acetylsalicylic acid, Aspirin(copyright))
2-methoxybenzoic acid
2,4-diacetoxybenzoic acid
2-hydroxy-4-aminobenzoic acid
2,4-dimethoxybenzoic acid
2,6-dihydroxybenzoic acid
2,6-dimethoxybenzoic acid
2,3,4-trimethoxybenzoic acid
2,4,6-trihydroxybenzoic acid and
2,4,6-trimethoxybenzoic acid
These compounds are known as such, commercially available and can be prepared by a person skilled in the art without problems. They show their particular therapeutic benefits, however, only in the compositions according to the invention.
A synergistic effect is not seen with all mixtures of the abovementioned benzoic acid derivatives. Whether a synergistic action may be present in a mixture can be easily determined by a person skilled in the art taking into account the details below.
Synergistic compositions are, for example, the following mixtures:
2,6-dihydroxybenzoic acid/2-hydroxy-4-aminobenzoic acid
2,6-dihydroxybenzoic acid/acetylsalicylic acid
2,6-dihydroxybenzoic acid/2,4-diacetoxybenzoic acid
2,6-dihydroxybenzoic acid/2,4-dimethoxybenzoic acid
2-hydroxy-4-aminobenzoic acid/acetylsalicylic acid
2-hydroxy-4-aminobenzoic acid/2,4-dimethoxybenzoic acid and
2,4-dimethoxybenzoic acid/2-acetoxybenzoic acid.
Furthermore, the following mixtures can also be mentioned:
2,4,6-trihydroxybenzoic acid/2,4-dimethoxybenzoic acid
2,4,6-trihydroxybenzoic acid/2,6-dihydroxybenzoic acid
2,4,6-trimethoxybenzoic acid/2,6-dihydroxybenzoic acid
2,4,6-trimethoxybenzoic acid/2-hydroxy-4-aminobenzoic acid
2,4,6-trimethoxybenzoic acid/2,4,6-trihydroxybenzoic acid
2,4,6-trimethoxybenzoic acid/2,4-dimethoxybenzoic acid.
As further mixtures can also be mentioned:
2-hydroxy-4-aminobenzoic acid/5-(2,4-difluorophenyl) salicylic acid
2-acetoxybenzoic acid/5-(2,4-difluorophenyl)salicylic acid
2-acetoxybenzoic acid/xcex1-cyano-3-hydroxycinnamic acid
5-(2,4-difluorophenyl)salicylic acid/xcex1-cyano-3-hydroxy-cinnamic acid and
2-hydroxy-4-aminobenzoic acid/xcex1-cyano-3-hydroxycinnamic acid.
The use of triple combinations of the mixtures is also especially preferred, whereby the following triple combinations have advantageous synergistic properties:
2-hydroxy-4-aminobenzoic acid/2-acetoxybenzoic acid/5-(2,4-difluorophenyl)salicylic acid
2-hydroxy-4-aminobenzoic acid/2-acetoxybenzoic acid/xcex1-cyano-3-hydroxycinnamic acid
2-hydroxy-4-aminobenzoic acid/5-(2,4-difluorophenyl)salicylic acid/xcex1-cyano-3-hydroxycinnamic acid and
2-acetoxybenzoic acid/5-(2,4-difluorophenyl)salicylic acid/xcex1-cyano-3-hydroxycinnamic acid.
In the abovementioned mixtures 2-hydroxybenzoic acid (salicylic acid) can also be used instead of acetylsalicylic acid.
An example which may be mentioned of a nonsynergistic composition of the above constituents is a mixture of 2,4-diacetoxybenzoic acid and 2-hydroxy-4-aminobenzoic acid.
On account of their pH sensitivity, the compositions according to the invention are only activated in cancer tumors and metastatic areas and therefore represent an ideal cancer therapeutic. It is also to be particularly emphasized that this novel cancer therapeutic acts generally on all tumor types independently of the specific type of cancer.
It is assumed that the substance mixtures according to the invention have toxic properties in the protonated state and act as cellular toxins on the tumors.
It is known that the pHs in the extracellular tumor tissue can be lowered again by about 0.5 pH units by inducing acidosis by glucose administration. Such an administration of glucose can likewise take place with the compositions according to the invention.
The compositions according to the invention can contain the active compounds in any desired proportions provided that the synergistic effect still occurs. How the activity of compounds and thus also the presence of a synergistic effect can be detected is described in detail, for example, in WO 96/30003, and in this respect reference can be made to this publication. Reference is further made to the following comparison examples.
The compositions according to the invention preferably contain the two active compounds in the ratio 1:9 to 9:1, particularly preferably in the ratio 2:1 to 1:2 and in particular in the ratio of approximately 1:1.
The synergistic activity of the compositions according to the invention was clearly confirmed by in vitro experiments. In the following, the following short forms are used for the following substance names:
The experiments according to the invention were carried out as follows:
The measurements were carried out using a xe2x80x9cCell Death Detection ELISA xe2x80x9d kit, Cat. No. 1774 425 commercially available from Boehringer (Mannheim). The process instructions are additionally supplied by Boehringer.
The results can be seen from Tables 1 to 3 below. The OD value corresponds to the cell death.
The results of the experiments are summarized in FIGS. 1 to 3, which correspond to Tables 1 to 3. In the figures, the cell death is recorded in a ELISA (apoptosis kit) with RT112 as a function of the pH. That is to say the data on the Y axis of the figures is a measure of the cell death; the pH of the cells is indicated on the X axis.